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Old Oct 22, 2010, 07:57 AM
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Dick, if you are interested take a look at the GLIDE product at eagletreesystems.com. The glide is the data collection unit. You can download current manuals even the desktop software from the site.

Roger
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Old Oct 22, 2010, 08:24 AM
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Dick is right- my time & resources are limited. If someone has an idea for their own test design & they are inclined to build a mechanized variable depth panel KF step wing & test it, by all means go right ahead! (I don't see myself personally having time & resources for that type of experiment anytime too soon- there are already many other projects & commitments.)

For me, finding time to build, and then taking some time to do some flying when air conditions are good is sometimes a bit of a challenge, as I'm typically backed up a couple of weeks on my business commitments.

Up here above 10,000 feet, winter is already settling in... snow is forecast for the next couple of days, with more by the middle of next week. I'll just have to see how much accumulates & stays. We may still see a few 'Indian Summer' days, but there may not be too many of them.

The snow surface typically becomes very wind-carved & irregular fairly rapidly here in South Park, so flying from it & landing on it out on Antelope Flats is seldom an option with most aircraft. I have a couple of fun fliers that deal with rough snow surface OK, but they are not designs which lend themselves to the wing design testing that I've been doing for the last couple of months.

A lot of the aircraft designing, building, & testing I already have in mind may be delayed unpredictably, and much of it will need to simply be spread out over time reaching into next year. For right now, the simplicity of simply taping an assortment of filler panels in place is serving my purposes very well- it's a very light weight & direct approach that costs next to nothing, and the changes can be implemented quickly between flights. Some days, keeping it simple is fine, too.

I'm sure that many of you also have time, resource, and commitment constraints that make it very unpredictable as to when you actually can complete a project of this nature. I wish each of you the best of success in your efforts!!

VIKING
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Old Oct 22, 2010, 09:52 AM
just Some Useless Geek
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Yes, Richard, that's a good approach. I was thinking more along the lines of a multi-axis, multi-planar approach, where both the step height and its position along the upper surface of the wing could vary. There might be some sliding, overlapping surfaces, just like on the real deal. The hinging mechanics involved would be considerably more complex, of course, but the controlling mechanism need not be too outrageous.
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Old Oct 22, 2010, 12:28 PM
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Multi-axis, multi-planar and multi-trouble . Issue is objective judging of effects and flight performance. Ideal would be onboard camera with OSD display like FPV guys use. You know - speed, altitude, vario, artifical horizon... But I guess that keychain camera shooting cotton strands taped to the wing will be used
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Old Oct 22, 2010, 04:36 PM
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Richard, Using an OSD is a terrific idea. Eagle tree has an OSD that would work, but I do not have it as I don't have the necessary FPV equipment (Camera, transmitter, and receiving hardware). If anyone has the hardware they would like to loan (I need 900Mhz as my receiver is on 2.4 Ghz), I will gladly try to get EagleTree to loan us the OSD hardware.

This is science on a budget. Neither money, supplies, or time is in abundance. We are doing the best with what we have. So if no one is willing to loan the hardware for the cause, my $10 keychain camera photographing the wool tufts and the FDR data readouts are what we will have to live with.

Roger
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Old Oct 22, 2010, 07:18 PM
Jack
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Roger,

I was looking at your eLogger data files and trying to figure out what you would have to do to get some meaningful data out of the logging. Unless I've missed something, the data you have available are:

Speed
Altitude
Rx_Volts
Pack_Volts
Pack_Amps
Watts

So that folks can see it, I have attached a captured image of about three minutes of the SS1-3.FDR file that Roger posted in that archive.

That starts right after launch and goes on from there for about three minutes. Maybe someone will spot a meaningful process in there and point it out?

Not sure why you have a negative altitude at the start and a couple of times during the flight either. Maybe you fly over declining terrain?

As with nearly any data stream like that, if you zoom in and look at the details it gives rise to a lot of questions. Some of it will go to vagaries in the data collection and recording equipment and other things too.

I have altitude, RPM, and temperature sensors (two of them) available for my eLogger V3 and find their use entertaining. I've started messing around with rewinding motors and the eLogger is really valuable there.

Anyone can download and install the Eagle Tree Data Recorder Windows application software but I'm not sure that you can see all the data displayed right or the same as Roger would if you do not have an eLogger. I say that because you select a model name at start up and that controls a bunch of settings as far as what it displayed and how it is displayed.

Eagle Tree has a Vendor's Forum here and does respond to questions and discussions there.

I have a feeling that part of the learning curve here is going to be that of figuring out what data to collect, how to collect it, and how to use the collected data.

Jack
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Old Oct 23, 2010, 08:56 AM
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Jack, I don't exactly know why the altitude starts out negative. I connected the plane's battery on a table about 3 feet off the ground. On when the FDR powered up the altitude records -4 feet. When placed on the ground before powering up the motor, the altitude shows -7 feet. I think it is all in the "acceptable limits of the altimeter.

I just counted and the SS1-3 file has 57 different "events" in the data. Over half are zero because there is no device attached to the FDR to record the data. For example there are four different RPMs recorded, the data from 4 servos, two temperatures, four G force readings, etc. The data also includes time from power up in 100 milisecond increments (1/10s of a second), event data, event error data, and a whole host of other things that we are not interested in.

In addition to what you displayed on your chart the GPS data including: GPSLat GPSLon GPSAlt GPSSpeed GPSCourse GPSDist could be of interest. The GPS altitude is MSL and is spot on. GPS Speed is of course ground speed. I will vary depending on the direction of the airplane relative to the wind.

I also just realized that I can collect throttle position information by connecting the ESC through one of the FDR servo data ports. That might be useful.

Roger
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Old Oct 24, 2010, 08:45 AM
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Roger,

You wrote before of comparing watts of input power required to fly a level course cruising at a specific selected airspeed with a variety of wing configurations. Getting a different readout of power requirement (watts) could then be attributed to that change in wing configuration (increase or decrease in total drag = increase or decrease in power required to cruise at the specific selected speed.)

That particular data collection & evaluation methodology seems very relevant and informative from my perspective. I haven't quite got to figuring out how all of the rest of the wide range of possible collectible data can be used in evaluating the aerodynamic affects of changes in KF step height & positioning on identical test wings (or on the same re-configurable test wing.)

Keeping the wing span, chord, and loading identical through all of the tests, as well as keeping the rest of the aircraft (motor, prop, battery, etc.) in a uniform configuration is a given. It also seems to me that if the fuselage has a lot of drag (stuff hangout in the air instead of being enclosed within a clean fuselage), then the slight changes in the wing configuration's drag contribution relative to the entire aircraft's drag will be a much smaller percentage, and therefore more difficult to evaluate.

VIKING
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Old Oct 24, 2010, 10:05 AM
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Viking, the watts and airspeed are the primary source of information. Other data help to level the playing field. As you know the airplane can maintain a given airspeed at different attitudes provided the correct power input. The altitude reading, for example, will tell us if we are in level flight, climbing or descending. For the relative drag equation we want to be in level flight. It may be level flight at very low alpha, or level flight at very high alpha. Both will be of interest. The GPS data help to keep the barometric data "honest". Keeping in mind that the GPS airspeed is in fact ground speed.

Yes, a high drag airframe will contribute a lot to the drag equation, but our wings are a major drag contributor as well. It is the nature of wings built from foam be they flat plate, or KF variants. This is one reason I plan to test with a "clean" airfoil wing. One that has our standard KF profile, but continues the curve to the trailing edge of the wing. This wing in theory will have considerably less drag, than any KF variant outside of what you are currently testing. Your test wing is fast approximating my clean wing.

It would be so nice if we only had a wind tunnel. Even a smoke tunnel would tell us a lot. Imagine being able to vary the KF geometry in a smoke tunnel while recording the info on video, or being able to get constant lift, drag, and moment data while varying the AoA and the geometry. All those wonderful numbers. It makes an ole engineer like me drool.

Come Spring we can start serious testing. Between now and then, we can sort out what the test rigs will have to be, and how the tests need to be performed. Sound reasonable?

Roger
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Old Oct 24, 2010, 09:19 PM
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Roger,

Sounds very reasonable! Thanks for everything you're doing on this!

VIKING
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Old Nov 01, 2010, 09:12 PM
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I've found that the placement of the step for optimum performance varies when it comes to exhilatation in the speed department with flying wings on the slope.

You can't ramp up the speed as fast, but with the KF you can hover it on the edge, unlike a curved fancy dancy airfoil.

..........results from a natural wind tunnel...............free to!

So, factor step placement into the equation.
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Old Nov 02, 2010, 01:33 AM
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Quote:
Originally Posted by jackerbes View Post
Not sure why you have a negative altitude at the start and a couple of times during the flight either. Maybe you fly over declining terrain?
Eagletree (and many others) altimeter measures barometric pressure, so It reads altitude above sea level rather than local ground level. Bad readings could be caused by calibration or temperature compensation issues, or some local pressure anomalies or sumthin' . Would be nice to have kind of sonar, to get actual height over pit/tree/house/... :P. I think that barometric sensors along with dynamic properties of barometric pressure (changes with height above sea level, changes with temperature, etc), yield poor altimeter for low altitudes. I fly only small models <1m, so I'd love some more accurate ground-altitude readings...

I'm brewing my own telemetry system around FrSky modules, so I hope to find something more usable.
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Old Nov 02, 2010, 04:03 AM
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kfm3 wing blu guppy video
Blu-Guppy Bergama'nın İlk Planörü PART-1 (9 min 0 sec)

very nice fly
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Old Nov 02, 2010, 01:48 PM
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Slope ships- from relaxing cruising to pure adrenalin!

Quote:
Originally Posted by goldguy View Post
I've found that the placement of the step for optimum performance varies when it comes to exhilatation in the speed department with flying wings on the slope.

You can't ramp up the speed as fast, but with the KF you can hover it on the edge, unlike a curved fancy dancy airfoil.

..........results from a natural wind tunnel...............free to!

So, factor step placement into the equation.
Frank,

I think that acceleration and 'ramping up the speed' have a lot to do mostly with wing loading, and also some to do with minimizing drag. And I also agree that placement of KF steps can become even more critical as flight speed increases. I'm also finding recently that shallower steps still provide the circulating vortex-trapping benefits, but with noticeably reduced drag = increased glide efficiency.

I'm tempted to build out my next prototype of the Me163-e as a pure slope ship, and build it as a fairly thin (~8% thick) KF3P build, possibly based on the RG14 or RG15 airfoil profile, but with a slightly reflexed trailing edge since this is more or less a flying wing. I'll start with the 48" panel size of the Bluecor PP as my starting wingspan, and shape out the up-swept extended wing tips which have been working so well on the original Komet. The upper wqing surface layers will be thinned to zero just into the base of those up-swept wing tips; they seem to have far less drag when they are a thin single layer with extensively thinned tip edges and trailing edges.

Since I want it to handle the heavy winds we sometimes see here high in the Colorado Rockies, I'll likely beef up the wing's spar structure, and also make provisions for carrying a variable ballast load centered on the CG which can be quickly adjusted to vary the wing loading from under 6 ounces per square foot up to about 15 ounces per square foot. I'll be flying totally with the elevons, no rudder on this build. I'll likely bury the servos & shroud the exposed elevon end of the linkages, and may even add the aileron gap cover strips to eliminate the elevon hinge line gap's drag contribution.

Why bother with all of this? I simply want to see just how 'slippery' of a KF variant wing I can really build. Flying 40 MPH+ winds with only a modest amount of ballast should be a fair confirmation of how cleanly a low depth stepped KF3P wing can be built & flown.

More soon!

VIKING
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Old Nov 02, 2010, 03:08 PM
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A forum member posted a quick comment:

Quote:
... "just having a step at somewhere 30-50% will work and you will not be able to tell the difference that the position has made."
[I posted this reply, which I thought was very relevant to this 'Technical Discussions" forum thread]:

What you have quickly summarized doesn't tell the whole story, and I'm sure we wouldn't want anyone to misunderstand, so I want to offer some qualification and additional information as 'food for thought'.

The affects of varying the placement of an added second flat layer of foam with a KF step at it's rear edge may not be as noticeable on a nutball, pizza box flier, or other very low aspect ratio fun flier design.

I want to add some extra information about aerodynamic factors that I've observed coming into play on some other types of aircraft with a higher aspect ratio wing. On some of these types of aircraft which I've built with KF stepped discontinuities added, it becomes very obvious that varying the positions (or adding extra material to change and extend the position of the primary KF step) does change the center of lift of the wing.

The reason for this is the underlying aerodynamic concept of a wing's "Camber Line". This is a line which originates at the center / entry point of the wing's leading edge, runs half way between the wings lower surface and it's upper surface, and extends to the center of the wing's trailing edge. A wing's camber is expressed as a percentage of chord; for a flat plate wing, it has a value of zero. The wing's 'chord line is a straight line which runs from the center of the leading edge's entry point to the center of the wing's trailing edge. But once you add a second layer of foam, etc. to a flat plate wing, and you add a KF step at it's rear edge, you shift the camber line.

Another significant aspect about a wing's camber is the % of cord at which the camber is at maximum. On a conventional airfoil, while the point of an airfoil's maximum thickness may generally be at roughly 30% of chord, the maximum airfoil camber is generally at closer to 40% of chord. [This can, of course, vary extensively, but these numbers are a good generalization for the purposes of this discussion.]

As you add camber to a wing, and a resulting point of maximum camber, you create a very significant influence on the resulting wing's Center Of Lift. On a flat plate wing to which a doubler layer has been added, terminating in a KF step, the point of maximum camber will be right at the KF step. And the location of the maximum camber will directly relate to the center of lift of the wing. If you change the point of maximum camber, you also change the center of lift.

An example: An RG14 airfoil wing of conventional built-up construction & covering displays optimum glide capabilities when the balance is at about 30% of chord. The early 2007 Dancer KFm variant wing was built to have a forward half profile similar to the RG14, with a step at 50% of chord. the resulting KF2 variant wing reached optimum glide performance with the CG adjusted to 39% of chord on this wing.

Understanding how shifts in a wing's maximum camber affect the wing's optimum center of lift is an important aspect of getting the most out of our KF variant aircraft designing & building projects; the results are reflected in how well these aircraft can fly.

VIKING
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